1. Field of the Invention
The present invention relates to an inkjet head and an inkjet recording device equipped with the inkjet head, as well as a method of anodically bonding silicon members and a method of manufacturing the inkjet head. The present invention particularly relates to a method of anodically bonding silicon members and method of manufacturing an inkjet head by anodically bonding the silicon members after an oxide layer has been formed on the surfaces thereof. These methods are capable of providing an anodically bonded member and an inkjet head that are resistant to the corrosive properties of various types of ink, including alkaline ink.
2. Description of the Related Art
Inkjet printers are widely used as personal color printers. Normally, these printers use water-based ink. Recently, however, wide-format printers have been used in industrial applications to print signboards, advertisements, and the like. In addition to water-based ink, these wide-format printers also use oil-based ink and solvent ink.
There has also been a trend toward using inkjet heads that employ piezoelectric elements such as PZT in industrial applications. Some examples of these applications are thin film forming devices used in the manufacturing of liquid crystal panels and other displays, interconnection patterning devices using metal nanopaste as ink, and devices for applying metal-catalyzed ink on fuel cells and the like. The ink used in these applications may be acidic, alkaline, polar solvent, and the like. In order to support these diverse types of inks, the components constituting the structure of the inkjet head, and particularly the components that come into contact with the ink, must be resistant to corrosion.
Further, in order to meet the demands for high quality and high resolution in the printing applications and demands for fine pattern printing in industrial applications, it is desirable to develop a high-density printing head capable of ejecting fine ink droplets of 10 picoliters (pL) or less with high precision. One method for meeting these demands is proposed in Japanese Patent Application Publication No. HEI-6-55733. This method proposes to produce parts constituting a print head structure by performing MEMS (Micro Electro Mechanical Systems) machining of silicon members.
Further, Japanese Patent Application Publication No. HEI-5-50601 proposes a method of joining the silicon member and glass substrate through anodic bonding instead of using adhesive for this bonding.
Japanese Patent Application Publication No. 2004-216747 proposes a method of manufacturing an orifice substrate, ink chamber substrate, and diaphragm substrate as components of the print head through dry etching of silicon material. An inkjet head is then produced by joining these substrates using anodic bonding.
Next, a conventional method of anodic bonding will be described in which two silicon members are bonded with glass interposed therebetween. In this description, two single-crystal silicon substrates are joined by anodic bonding. First, a silicon dioxide (SiO2) layer is formed on a surface of one silicon substrate, and a layer of borosilicate glass is formed in turn on the surface of the silicon dioxide layer.
Next, the three-layer substrate comprising the silicon substrate, silicon dioxide layer, and borosilicate glass layer is laminated over the other single-crystal silicon substrate so that the borosilicate glass layer contacts the other substrate. The three-layer substrate and the other silicon substrate are bonded anodically by applying heat and electricity to the laminated structure.
The method of manufacturing an inkjet head disclosed in Japanese Patent Application Publication No. 2004-216747 uses the anodic bonding method described above. In this method, single-crystal silicon is subjected to dry etching to form an orifice substrate, ink chamber substrate, and diaphragm substrate. The surfaces of the orifice substrate and diaphragm substrate are then subjected to an oxidation treatment at temperatures over 1000° C. to form a silicon dioxide (SiO2) layer on the surfaces of the substrates. Next, a borosilicate glass layer is formed on the surface of the silicon oxide layer on the side to be joined with the ink chamber substrate. The orifice substrate and ink chamber substrate are then joined through the anodic bonding method described above. Similarly, the ink chamber substrate and diaphragm substrate are joined by the anodic bonding method, thereby producing the inkjet head.